Hi Mad,
It's almost impossible to "protect" speakers with a fuse arrangement because of the highly dynamic audio signals from some types of music and movie soundtracks, the problem being the fuse blowing on dynamic peaks when you the last thing you want is a cessation of the musical peak.
Besides, a fuse will not protect the drivers from dirty clipped amplifier signals. The M80s are capable of handling many hundreds of clean, unclipped amplifier watts on peak dynamic signals without damage or distortion. We've tested the M80s to beyond 700 watts per channel with no damage.
I suppose some speakers with poor peak power-handling characteristics might benefit from fusing, but the vast majority of high-quality speakers do not have fuses.
If Ian sees this post, he may want to weigh in on the issue of speaker fuses.
Regards,
Alan
